Alleged killer Lucy Letby is said to have murdered one baby by injecting air into his stomach.
The shocking revelation comes as details of the former nurse's murder methods have come to light as the trial enters its second day at Manchester Crown Court.
The former nurse is charged with seven counts of murder and fifteen counts of attempted murder.
Lucy Letby, 32, allegedly carried out a year-long killing spree from June 2015 while working at the Countess of Chester Hospital in Chesire, UK.
The suspicious deaths that occurred between June 2015 and 2016 were initially investigated in May 2017.
In total, five girls and two boys died, while another five girls and five boys were saved by a team of doctors and nurses.
Over the last day, Manchester Crown Court heard shocking details on the cause of deaths surrounding child A and C and how the murderer honed her killing method over a single week.
The families of victims heard that Letby killed her first baby by injecting air into the boy's bloodstream, before changing her deadly method just six days later on Child C when she forcibly injected air into a baby's stomach via a nasal gastric tube.
The 32-year-old from Hereford has denied all murder charges, including fifteen counts of attempted murder.
While the babies cannot be named for legal reasons, family members of the victims were present in the public gallery at the trial's opening.
The trial continues at Manchester Crown Court.
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